C2C12 cells were transfected with siRNA against BMP receptor type I (ALK2, ALK3, ALK5, ALK6), BMP receptor type II (BMPR-II, ACTR-IIA, ACTR-IIB) and β chain integrins (β1, β3, β5) and plated on soft (light color) and rigid (dark color) films with bBMPs for 5 or 4 h, respectively. (a) pSMAD1,5,9 signal and (b) ALP activity were quantified, and the relative % is given, in comparison to a control scrambled siRNA. Data represent the mean ± SEM. Statistical tests were done using non-parametric Kruskal-Wallis ANOVA test (*, p ≤ 0.05; **, p ≤ 0.01). Statistical comparisons were made between soft and rigid films for each condition.